wear one's heart upon one's sleeve

Verb

wear one's heart on one's sleeve (third-person singular simple present wears one's heart on one's sleeve, present participle wearing one's heart on one's sleeve, simple past wore one's heart on one's sleeve, past participle worn one's heart on one's sleeve)

1. (idiomatic) To be very transparent, open, or forthright about one's emotions.
   • Iago: For when my outward action doth demonstrate
     The native act and figure of my heart
     In compliment extern, 'tis not long after
     But I will wear my heart upon my sleeve
     For daws to peck at: I am not what I am.c. 1603–1604 (date written), William Shakespeare, “The Tragedie of Othello, the Moore of Venice”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac...

   Synonyms:

   to be an open book